This invention relates to projection lamps and more particularly to a lamp collar having integral vanes that allow air to circulate within and flow through the lamp reflector to cool and maintain the temperature of the lamp.
Image projection systems are becoming increasingly popular for conducting sales demonstrations, business meetings, and classroom instruction. Such image projection systems typically receive analog video signals from a personal computer (PC). The video signals may represent still, partial-, or full-motion display images of a type rendered by the PC. A projection engine of these projection systems includes a light source, an image-forming device, and optical components for directing images onto a screen. The light source typically includes a replaceable lamp module for generating and directing light toward the image-forming device before it is projected onto the screen. In order to produce adequate light intensity, the lamp module includes a light source which may be, for example, a metal-halide or other type of arc lamp, an incandescent lamp, or a fluorescent lamp.
Such image projectors are becoming smaller, more compact, and lighter weight so that they can be carried by one person. The light source operates at high temperatures and must be cooled to prevent damage to the image projector. This is particularly important in smaller image projectors where the components are arranged in a compact manner.
Typical image projection lamp assemblies include a lamp located within a reflector. This assembly is usually positioned within the projector housing near the projection engine by a ceramic collar to which the reflector is attached. The ceramic collar is typically bonded to a front periphery of the reflector with a ceramic-type cement. The ceramic collar is used to locate the lamp assembly within the projector housing such as, for example, by nesting within locator projections on the projector housing.
Heat is produced by the lamp, which typically includes a front-arm and a back arm. The back arm of the lamp connects it to the reflector so that the front arm extends into the reflector. Heat is generally produced under high pressure by the front arm of the lamp, and it is important to keep the temperature of the lamp from exceeding an upper limit to prevent damage to the image projector. Additionally, a temperature differential may develop within the lamp itself. This occurs because heat naturally rises, causing the top of the lamp to become hotter than the bottom of the lamp. Therefore, it is important not only to cool the lamp but to maintain a substantially constant lamp temperature.
Image projection systems typically include a fan to produce an air flow across the lamp assembly to cool it. The lamp assembly is usually located within the projector housing so that the fan blows a directed flow of air across the lamp assembly and out through exhaust openings. The air is generally circulated over and around the reflector. Some of the air may flow into the reflector but any such air is negligible and may not be enough to cool the lamp or maintain a constant lamp temperature. Generally, no air is directed into the reflector to directly flow across the lamp and/or circulate within the reflector.
It is therefore desirable to provide a lamp assembly in which cooling air is directed into the reflector to flow across the lamp and to circulate within the reflector to cool the lamp and maintain a substantially constant lamp temperature.
It is an object of the invention to provide a lamp assembly that is suitable for use in portable and compact image projectors.
Another object of the invention is to provide a lamp assembly in which the lamp is cooled and maintained at a substantially constant temperature by a directed flow of air.
Yet another object of the invention is to provide a lamp assembly that is configured to allow a flow of cooling air into and through the reflector.
A further object of the invention is to provide a collar for the lamp assembly that includes integral vanes to direct cooling air into and through the reflector.
A lamp assembly of the present invention includes a lamp collar for locating the lamp assembly within an image projector housing. The lamp collar is attached to a front periphery of the reflector and cooperates with locating features on the image projector housing to position and secure the lamp assembly within the image projector housing. The lamp assembly is preferably located adjacent the projection engine. In order to cool the lamp assembly a cooling device such as a fan is located adjacent the lamp assembly so that a cooling flow of air is directed across the lamp assembly.
The lamp collar includes integral vanes that allow air to flow into and through the reflector to cool the lamp. The vanes direct the air to flow along different paths to various parts of the reflector interior. The directed air flow serves to cool the front arm of the lamp and to maintain a substantially constant lamp temperature. Some of the air is directed to flow across the front arm of the lamp to cool it and then flows out of the reflector through an exhaust opening in the lamp collar. Air is also directed along paths to circulate within the reflector before exiting the reflector through the exhaust opening.
The shape of the vanes may vary depending on the where within the reflector the air flow is most desired. Generally, the vanes have the shape of an air foil. In some instances it may be desirable to provide a cut-out portion in the reflector at a location adjacent the vanes to increase the amount of air flowing around and through the reflector.
Additional objects and advantages of this invention will be apparent from the following detailed description of preferred embodiments thereof which proceeds with reference to the accompanying drawings.